Multilayer ceramic coil and motor using the same

ABSTRACT

A multilayer ceramic coil ( 4 ) for use in a compact motor is configured so that ceramic layers ( 4   c ) having a plurality of coil patterns ( 4   a ) and ( 4   b ) printed using a conductive paste are laminated, and that the coil patterns in respective layers are electrically connected via thru-holes ( 4   d ) to form a single multilayer ceramic structure having a plurality of phases of patterned-coil.

BACKGROUND OF THE INVENTION

1. Technical Field

The present invention relates to a multilayer ceramic coil and a compactmotor (hereafter referred to motor) using the same.

2. Background Art

As shown in FIG. 4, a typical conventional brushless motor comprises

a plurality of coils 34 fixed on printed board 36 by soldering, andmagnet 35 fixed on rotor frame 32 and opposing coils 34 across a gap.

A brushless motor of the above configuration has been provided withcoils wound by metal wire. Nowadays, however, along with recent advancesin printed wired board technology, a different coil manufacturing methodis disclosed, e.g., in the Japanese publication of patent applicationNo. S57-68565, No. S57-186940, No. S57-68656 or No. S58-33958. In thismethod, a printed pattern of a conductive coil pattern is applied onfilm 40 composed of epoxy resin, polyester resin and polyimide resin orthe like to form coil sheet 44, and laminate a lot of those coil sheets44 to form a multilayer coil, as shown in FIG. 5.

Such multilayer coil is advantageous to make a compact motor because aconventional core wound by metal wire is not necessary and wire windingdensity is high.

But the conventional multilayer coil mentioned above needs an additionalprocess to apply an adhesive layer evenly on a plurality of respectivecoil sheets 44 for bonding, which results in the problem of highproduction costs.

Additionally, the coil sheet composed of plastic or composite materialshas a poor thermal resistance and is easily affected by ambienttemperature. Therefore, operation conditions such as the ambienttemperature for a brushless motor must be restricted to prevent anunstable movement caused by heat generation due to copper loss and ironloss.

Consequently, in order to solve the above problems of the conventionalmultilayer coils, a method of manufacturing a coil configuration isdisclosed in the Japanese publication of patent application No.H5-336712 which, as shown in FIG. 6, includes:

(a) forming a conductive coil pattern on a glass substrate,

(b) providing the conductive coil pattern with a glass coating, and

(c) forming a conductive coil pattern further on the glass coating, and

finally, applying a glass coating on the top surface to produce amultilayer coil.

Generally, however, the glass used for such multilayer substrate hasdrawbacks of low impact resistance and a short performance life.

SUMMARY OF THE INVENTION

Therefore, a multilayer ceramic coil is proposed to include a pluralityof ceramic layers having coil patterns printed with conductive paste,wherein the coil patterns of respective layers are electricallyconnected via thru-holes, and wherein the ceramic layers are laminatedto form a single multilayer ceramic structure comprising a plurality ofphases of coil.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view of a motor used in an exemplaryembodiment of the present invention.

FIG. 2A is plan view of patterns of a multilayer ceramic coil used inthe exemplary embodiment of the present invention.

FIG. 2B is a cross-sectional view of a multilayer ceramic coil used inthe exemplary embodiment of the present invention.

FIG. 2C is an outline view of a multilayer ceramic coil used in theexemplary embodiment of the present invention.

FIG. 3 is an exploded perspective view of a coil pattern for one phaseof the coil pattern used in the exemplary embodiment of the present.

FIG. 4 is a cross-sectional view of a conventional motor.

FIG. 5 is an exploded perspective view of a multilayer ceramic coil of aconventional motor.

FIG. 6 is an exploded perspective view of a multilayer ceramic coil ofanother conventional motor.

DETAILED DESCRIPTION OF THE INVENTION

The present invention is described by following preferred embodimentwith reference to drawings.

Exemplary Embodiment

FIG. 1 shows a motor used in an exemplary embodiment of the presentinvention. A cross-sectional view of the motor is shown in FIG. 1. Asshown in FIG. 1, rotation axle 1, having a rotation axis, is secured torotor frame 2 and is disposed perpendicular thereto. Multilayer ceramiccoil 4 is fastened on bearing 3 by means of a housing 7. Bearing 3 holdsthe rotation axle rotatably. Magnet 5 is secured on rotor frame 2 andopposes multilayer ceramic coil 4 across a gap G.

Delivering excitation current to multilayer ceramic coil 4, and thuscausing attraction and repulsion of the magnet with respect tomultilayer ceramic coil 4 produces a rotating force of the motor.

FIG. 2A is a plan view of configurations (patterns) of multilayerceramic coil 4, FIG. 2B shows a cross-sectional view of the multilayerceramic coil, and FIG. 2C shows an outline view of the multilayerceramic coil 4.

Coil patterns 4 a and 4 b printed on ceramic layer 4 c are electricallyconnected alternately via thru-holes 4 d. Phases of coil patterns 4 aand 4 b are electrically connected to phases of crossing pattern 4 e,respectively.

In addition, each phase terminal is electrically connected to outletelectrode 4 g by means of terminal pattern 4 f. Outlet electrodes 4 gare mounted at four corners of multilayer ceramic coil 4. Outletelectrodes 4 g are soldered on printed wired board 6 to securemultilayer ceramic coil 4 on the board.

Next, a procedure to form a coil pattern on multilayer ceramic isdescribed in detail by setting forth process steps (a)–(g) withreference to FIG. 3. FIG. 3 is an exploded view of a winding formationfor one phase of multilayer coil pattern.

-   -   (a) Connect individual terminal pattern 51 electrically to a        winding top of coil pattern 53 a, formed on a layer one layer        below, via thru-hole 52 a.    -   (b) Connect winding end of coil pattern 53 a electrically to a        winding top of coil pattern 53 b of the formation, formed on a        layer further one layer below, via thru-hole 52 b.    -   (c) Laminate coil patterns 53 a and 53 b from top to bottom to        form patterned-coil 55 a in this way, via thru-holes 52 a and 52        b.    -   (d) Similarly, laminate coil patterns 53 a and 53 b from bottom        to top to form patterned-coil 55 b, via thru-holes 52 a and 52        b.    -   (e) Moreover, connect a winding end of coil pattern 53 a on the        bottom layer of patterned-coil 55 a electrically to one end of        crossing pattern phase 54, formed on a layer further one layer        below, via thru-hole 52 b.    -   (f) Connect another end of crossing pattern phase 54        electrically to a winding top of coil pattern 53 a, formed on        the bottom of patterned-coil 55 b, via thru-hole 52 a, to        provide patterned-coil 55 a and patterned-coil 55 b with an        electrical.    -   (g) Finally, connect a winding end of coil pattern 53 a on the        uppermost layer of patterned-coil 55 b electrically to common        terminal pattern 56 via thru-hole 52 b to provide a        patterned-coil having multiple outlet electrodes.

The multilayer ceramic coil disclosed in the present invention has sucha configuration that conductive coil patterns are embedded and laminatedin a multilayer ceramic structure to provide a coil formation to whichexcitation current of the motor is fed, which can solve problems of theconventional art.

The multilayer ceramic coil has a plurality of ceramic layers havingcoil patterns printed using conductive paste, connected to the coilpatterns of respective layers electrically via thru-holes and laminatedto form a single multilayer ceramic structure including a plurality ofphases of patterned-coil. In addition, terminals of coil patterns formedinside of the multilayer ceramic structure are electrically connected tooutlet electrodes disposed on surrounding surfaces of the multilayerceramic coil to form terminals for feeding excitation current for themotor.

The present invention is not limited to the exemplary example mentionedabove but can be used for various applications within the concept ofthis invention.

As mentioned above, the multilayer ceramic coil for use in a motoradopts ceramic as an innovative coating material. A motor equipped withthe multilayer ceramic coil generates a stable torque force because themultilayer ceramic coil has a higher thermal resistance compared withcoils provided by plastic, composite materials or glass and has a goodheat conductivity. Additionally, the motor shows a reliable performancein various ambient conditions.

INDUSTRIAL APPLICABILITY

The present invention discloses a multilayer ceramic coil and a motorusing the same. A multilayer ceramic coil for use in the motor isconfigured with conductive coil patterns embedded and laminated in amultilayer ceramic structure to provide a coil formation to whichexcitation current for the motor is supplied.

1. A motor comprising: a multilayer ceramic coil formed by a pluralityof laminated ceramic layers on which patterns are printed, said patternsbeing formed of conductive paste; wherein said multilayer ceramic coilincludes a first ceramic layer having a plurality of electricallyindependent coil patterns printed thereon, said coil patterns beingformed of conductive paste, a second ceramic layer having an electricalcrossing pattern printed thereon, said crossing pattern being formed ofconductive paste, and a third ceramic layer having a terminal patternprinted thereon, said terminal pattern being formed of conductive paste;wherein said first, second and third ceramic layers are arranged so asto constitute a single multilayer ceramic structure having a pluralityof phases of coils, and wherein said coil patterns, said crossingpattern, and said terminal pattern are electrically connected viathrough-holes in said ceramic layers; and wherein said terminal patternof said third ceramic layer is formed with a common terminal and with aplurality of individual terminals equal in number to said plurality ofphases of coils, said terminal pattern being electrically connected toeach of said coil patterns.
 2. The motor of claim 1, wherein said firstceramic layer of said multilayer ceramic coil comprises a plurality oflaminated layers.
 3. The motor of claim 1, wherein said second ceramiclayer is disposed at an end of said plurality of laminated layers ofsaid first ceramic layer.
 4. The motor of claim 1, further comprising aplurality of outlet electrodes respectively connected to said individualterminals of said terminal pattern.
 5. The motor of claim 1, furthercomprising a rotor frame rotatably mounted to said multilayer ceramiccoil.
 6. The motor of claim 5, further comprising a bearing mounted tosaid multilayer ceramic coil and rotatably supporting said rotor frame.7. The motor of claim 5, further comprising a magnet mounted to saidrotor frame and being disposed opposite said multilayer ceramic coilacross a gap.